scratch_alloc() set scratch_start to the last byte of the current
allocation. The value of scratch_start is then reused as is (if it is
already aligned) in the next allocation. This result in a potential reuse
of the last byte of the previous allocation.
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>